Many different medical procedures are performed that require the stabilization of adjacent bone sections or bone portions through the securing of an interbody spacer to the adjacent bone portions. Examples of these spacers are known to those in the field as interbody cages, corpectomy cages, osteotomy wedges, joint spacers, and bone void fillers, among other names and labels.
As one example, spacers are used to fuse bone joints. Spacers are also used to repair complex fractures where bone is missing and in bone regions where there are voids within the bone structure, such as when a tumor and adjacent bone may be removed. Spacers are also used in the performance of osteotomies by placing the spacers between adjacent bone portions to perform a wedging action, including to straighten a bone. These are but a few examples of, and are an not exhaustive description of the medical procedures that require the placement of a spacer between adjacent bone portions.
In each procedure, the spacer placed between the bone portions is required to be rigidly joined to the adjacent bone portions. A multitude of different apparatus have been designed for this joinder purpose. One example of connecting or joining a spacer to adjacent bone structure is through the use of insertion screws. While screws are generally effective for this purpose, they are limited in the sense that they do not afford stability in all orthogonal dimensions often required to effect the optimal or desired rigidity.
Spacers are also commonly used in spinal repair and reconstruction. The spine is a flexible column formed of a plurality of bones called vertebra. Each vertebrae are annular-shaped structures having a hard cortical bone on the outside and porous cancellous bone on the inside. The vertebrae are stacked, in column fashion, one upon the other, forming a strong annular column supporting the cranium and trunk. The core of the spine protects the nerves of the spinal cord. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibro-cartilaginous bodies.
The intervertebral fibro-cartilages are also known as intervertebral disks and are made of a fibrous ring filled with pulpy material. The disks function as spinal shock absorbers and also cooperate with synovial joints to facilitate movement and maintain flexibility of the spine. When one or more disks degenerate through accident or disease, nerves passing near the affected area may be compressed and are consequently irritated. The result may be chronic and/or debilitating back pain. Various methods and apparatus have been designed to relieve such back pain, including spinal fusion using a suitable graft or interbody spacer using techniques such as Anterior Lumbar Interbody Fusion (“ALIF”), Posterior Lumbar Interbody Fusion (“PLIF”), or Transforaminal Lumbar Interbody Fusion (“TLIF”) surgical techniques. The implants used in these techniques, also commonly referred to as an intervertebral spacer, are placed in the interdiscal space between adjacent vertebrae of the spine.
Ideally, a fusion grant should stabilize the intervertebral space and become fused to adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the graft should have sufficient structural integrity to withstand the stress of maintaining the intervertebral space without substantially degrading or deforming. The graft should also have sufficient stability to remain securely in place prior to the time of actual bone ingrowth fusion.
One significant challenge to providing fusion grant stability (prior to actual bone ingrowth fusion) is preventing spinal extension that may result during patient movement. Distraction of the vertebral space containing the fusion graft may cause the graft to shift or move, which in turn may result in disrupting bone ingrowth fusion and causing pain.
Current and existing spinal fusion technology has been limited, and is lacking in certain respects relating to the above described issues. Among the limitations of certain of these systems is the requirement that complicated steps need to be performed to accomplish their proper use. As noted, others of these type of devices and systems, included screws, and lack the optimal multi-dimensional stability, while others are less than desirable because they use components that may project externally of one or more of the bone portions between which the spacer is located. Other deficiencies and problems also exist with respect to prior devices and systems.
The systems that rely upon the use of screws may have certain limitations. Such systems may not effectively allow compression forces to be generated between the spacers and adjacent bone portions. Further, while the screws do stabilize the bone-spacer junction in one plane, that is normally flexion-extension, they may not, in certain applications, control bending in another plane or direction that is orthogonal to the plane of the screw.
A further problem with existing systems is that components or parts typically are often not locked in place and are thus prone to working loose over time. Screws, for example, may loosen over extended usage and time in the absence of incorporating some structure that effectively prevents turning or lengthwise movement. Without such locking elements, a loosened screw could result in partial or full separation of the device from the bone portions and/or spacers that they penetrate.
Several disc spacer devices have been designed and proposed to address some of these noted limitations. Examples include U.S. Pat. No. 6,569,201 for a Hybrid Composite Interbody Fusion Device, issued to Moumene et al.; U.S. Pat. No. 7,776,093 for a Vertebral Body Replacement Apparatus And Method, issued to Wolek et al.; and U.S. patent application Ser. No. 11/643,994 for an Interbody Fusion Hybrid Graft. In addition to these devices, the medical field is constantly seeking system designs that might be efficiently and consistently installed and that, most significantly, will affect the desired fusion in a manner that will be safe and reliable for the patient. The various embodiments of devices and methods described in this application address such a need.